DNA BINDING STUDIES OF MAGNESIUM(II), CALCIUM(II), BARIUM(II) AND ATP COMPLEXES

Publisher Website
Google Scholar
Abstract
We have investigated the ways by which magnesium (II), calcium (II) and barium (II) and their ATP complexes bind to B-DNA. Effects on native calf thymus DNA conformation were studied and compared with those involving the uncomplexed metal ions and the polymer. It was found that MgATP−2, CaATP−2 and BaATP−2, interact with the phosphates of the polynucleotide; only BaATP −2 appears to bind also through the bases. ATP complexes cause transitions mainly to the B family. The C form is induced by small amounts of MgATP −2 or CaATP−2. At high complex concentrations (r = 2.5 or 5) the polynucleotide adopts the ψ conformation, while BaATP−2 induces this transition at r = 0.6. A contribution of the A form is observed in the case of CaATP-DNA at r = 0.6 and at the beginning of the reaction in the Ba-DNA system at 22°C, for r = 5. The alkaline earth metal ions induce a stabilization of the B conformation. Structural changes with magnesium (II) at r = 2.5 are interpreted in terms of a B to C transition. Calcium (II) at r = 5 produces the A form. In other cases the alkaline earth metal ions stabilize the B conformation. It was found that they all interact with the phosphates of the polynucleotide. The binding ratio, r, is an important factor in all structural changes.